"The incidence of AF is highest in the first 60 to 90 days after a breast cancer diagnosis," Dr. Avirup Guha of Case Western Reserve University in Cleveland, Ohio, told Reuters Health by email. "AF after breast-cancer diagnosis increased cardiovascular mortality, and cancer severity (stage/grade) is a strong risk factor for the development of AF."
Dr. Guha and colleagues' findings were reported at the American Heart Association Scientific Sessions, with simultaneous publication in the European Heart Journal.
The findings are based on more than 85,000 women aged 66 or older who were diagnosed with breast cancer between 2007 and 2014. Among these, 9,425 (11%) had a pre-existing AF diagnosis before their breast-cancer diagnosis.
New-onset AF occurred in 2,993 (3.9%) women in the one-year period after breast-cancer diagnosis. In contrast, only 1.8% of matched women without breast cancer developed AF over the same one-year period.
The rate of new-onset AF in women with breast cancer was highest in the first two month after their cancer diagnosis and was higher among older women and Black women.
Breast-cancer severity (stage and grade) was strongly associated with the risk of AF onset, "with over 300% higher likelihood of AF" in those with stage-IV versus stage-I breast cancer, Dr. Guha and colleagues report in their paper.
Women with breast cancer who did not receive initial surgery, radiation or hormonal therapy were at higher risk of developing AF than those who received these treatments.
"This finding is potentially related to the fact that those with higher-stage cancer, which is related to a higher risk of AF, are likely to receive systemic chemotherapy as first-line treatment," the researchers say.
"Remarkably, left-sided breast cancer and breast cancer subtype based on receptor status (HER2Neu/HR) were not associated with AF risk," they report.
AF risk was higher with complex surgeries such as mastectomy than simple surgeries such as lumpectomy. Brachytherapy was associated with a lower risk of AF onset than external beam radiation, likely owing to the lower cardiac dose from radiation implants into the breast.
"Notably," the authors write, use of cardiovascular medications such as beta-blockers, angiotensin-converting-enzyme inhibitors/angiotensin-receptor blocker, and spironolactone/eplerenone appeared to lower the risk of developing AF.
"In fully adjusted models, mortality in breast cancer patients is higher at one year among those who have new-onset AF after a breast cancer diagnosis, and this mortality risk is predominantly cardiovascular and not related to breast cancer," they report.
It's "hard to conclude that we need to monitor breast-cancer patients after diagnosis using a retrospective study," Dr. Guha told Reuters Health. However, "we adjusted for prior use of CV (cardiovascular) medication before AF diagnosis in the mortality model and we noticed increased all-cause mortality and CV mortality despite that."
"Those with existing AF did not have an increased risk of mortality after breast-cancer diagnosis compared to those who did not develop AF. This may be because they were already well managed from a CV standpoint. Thus, I speculate that the involvement of cardio-oncology in the care of breast cancer patients may mitigate the mortality outcomes noted in this study," Dr. Guha said.
Strengths of the study include the large sample size and ethnic diversity of the population. Limitations include that it only looked at women aged 66 and over, meaning the results may not apply to younger women.
Also, the study is based on medical claims data, the prevalence of obesity may have been under-reported and the study followed patients for only one year.
SOURCE: https://bit.ly/30xuZME European Heart Journal, online November 14, 2021.
By Megan Brooks
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